Electric power controlling apparatus

ABSTRACT

An electric power controlling apparatus, wherein the time for which electric power is supplied to a load is determined in accordance with a change of the charging or discharging time of a capacitor, the amount of power to be supplied to said load is determined in accordance with a change of the trigger phase of a thyristor, and said changes are achieved by selecting variable elements by the use of pushbutton switches.

United States Patent Hosokawa et al.

ELECTRIC POWER CONTROLLING APPARATUS Inventors: Tomoyuki Hosokawa,Takarazuka-shi;

Chuzo Wada, Osaka; Hiroshi Horii, Takatsuki-shi, all of Japan Assignee:Matsushita Electric Industrial Co., Ltd.,

Osaka, Japan Filed: Nov. 24, 1969 Appl. No.: 879,188

Foreign Application Priority Data Nov. 25, i968 Japan ..43/85605 US. Cl..3l8/484 Int. Cl. ..H02p 5/16. Field ofSearchW, ..318/305, 341, 345,331, 484,

1451 Jan. 25, 1972 Primary Examiner-Bernard A. Gilheany AssistantExaminer-Thomas Langer Attorney-Stevens, Davis, Miller and Mosher 5 7]ABSTRACT An electric power controlling apparatus, wherein the time forwhich electric power is supplied to a load is determined in ac cordancewith a change of the charging or discharging time of a capacitor, theamount of power to be supplied to said load is determined in accordancewith a change of the trigger phase of a thyristor, and said changes areachieved by selecting variable elements by the use of pushbuttonswitches.

6 Claims, 11 Drawing Figures u|||@|,. 49 l l %50 0 1:1" 65 7375 7779 A?/0 a I k 74767860 465 42 66192 1 l 2 2 A /57 541N553 43' 25 p 7/ l 1 5/62 5a 60 1 I 9/ 1 a r I I," 64 7 1 306/ illliiillillil '1'1'1'1 d -""8""r 8284866890 g?? a3 a5 8789 PATENTED JANZS 1372 saw u or 5 KN MK MN kW H1H PATENTED JANZS m2 SFIEU- 5 OF 5 ELECTRIC POWER CONTROLLING APPARATUSThis invention relates to improvements in or relating to an electricpower controlling apparatus wherein a predetermined amount of power iscontinuously or intermittently supplied to a load for a predeterminedperiod of time.

There have conventionally been proposed electric powercontrollingapparatus wherein application of electric power to a load is controlledby adjusting the trigger phase of a thyristor and the release of thepower application is effected by means of a'time-limit device. In suchconventional apparatus, however, the power control is effected byturning a pointer (over a graduated dial), and the time-limit deviceuses a spring or a motor.

However, the amount of power and power supplying time should be setevery time the apparatus is used, and it is often the case thatdifferent values should be set each time the apparatus is used.Furthermore, the apparatus should be newly set even when the same setvalues are repeatedly used. Therefore, the aforementioned conventionalapparatus is disadvantageous in that great inconvenience is involvedinusing the same and it is impossible to achieve a high accuracy.

Referring to FIGS. 1 and 2, there is shown such a conventionalapparatus, wherein a closed circuit is constituted by an AC power source120, spring-type timer 12], load 122 and power control apparatus 123.The operating panel of the timer 121 is as shown in FIG. 2, wherein inorder to set up a time limit, a pointer 124 is turned into registry withthe corresponding one of the numerals indicated on a dial plate 125.Fine graduation is provided on the dial plate I25 in addition to thenumerals. In the case where a time limit with a high accuracy isrequired to be set up, it isnecessary to preciselyset the thumb to thegraduation. Although in the foregoing, description has been made of thecase where the spring-type timer l2l'is used, the above is also true inthe casewhere a motor is used instead of the spring. In either case, itis required that the pointer 124 be turned to set up a desired timelimit every time the apparatus is used. In an attempt to usesuch aconventional apparatus repeatedly, great inconvenience is involved inhandling the same, and still it is impossible to obtain high accura- Thepresent invention is characterized in that the time for which electricpower is supplied to a load is deten'nined in accordance with a changeof the charging or discharging time of electric power-controllingapparatus wherein'a DC power source, timer circuit and gate circuit 'fora thyristor are separated from an AC power source by energizing a relaywith the output of the timer circuit so that the. power supply to a loadcan be safely effected with the aid of the relay having a low capacity,whether the load is high or low.

Another objectof the present invention is to provide an electricpower-controlling apparatus wherein the output terminals of a gatecircuit rendering a thyristor conductive are short-circuited with theoutput of a timer circuit, and the short-circuiting can be effected bythe use of switching elements or switching circuits of a low capacitybecause of the fact that the gate pulse is constituted by a low voltageand current.

Another object of the present invention is to provide an electricpower-controlling apparatus wherein a bridge circuit is constituted by atime-constant series circuit of a resistor and capacitor and a seriescircuit of two resistors. The connection point between the resistor andthe capacitor is connected to the base of a transistor and theconnection point between the two resistors is connected to the emitterof the transistor, the capacitor or resistor of said time-constantcircuit being changed by'selecting elements having different values bymeans of pushbutton switches. The time limit is made to be proportionalto the value. of the resistor or capacitor of the time-constant seriescircuit, thereby facilitating the time setting and minimizing variationsof the set time due to variations of the power source voltage.

A further object of the present invention is to provide an electricpower-controlling apparatus wherein the resistor of a time-constantseries circuit incorporated in the aforementioned timer circuit isconstituted by a plurality of resistors connected in series with eachother, normally closed switches are connected in parallel with saidplurality of resistors, and said switches are opened in suitablecombinations to achieve a number of combinations of resistors, therebyadding the set time limits so as to provide a great number of controltime limits by using a small number of buttons.

A further object of the present invention is to provide an electricpower-controlling apparatus wherein a transistor'l, which is renderedconductive by a signal available from a time-constant circuitincorporated in a timer circuit to charge a capacitor and a transistorwhich is rendered conductive by the discharge of the capacitor areconnected in parallel with each other, whereby a thyristor is shortcircuited betweenthe' gate circuit thereof and a first electrodethereof, and the short circuit is miniaturized, simplified in assemblyand of a high durability.

A still further object of the present invention is to provide anelectric power-controlling apparatus wherein there is provided anintegrating circuit constituted by a resistor and capacitor, a triggerelement operating a thyristor is operated by a voltage appearing at theconnection point between the resistor and the capacitor, said resistoris constituted by a plurality of series circuits of normally openswitches and resistors having different values which are connected inparallel with each other, and the amount of power supplied through thethyristor is easily and accurately controlled by actuating pushbuttonswitches.

Other objects, features and advantages of the present invention willbecome apparent from the following description taken in conjunction withthe accompanying drawings, in which;

FIG. 1 is a diagram showing the circuit arrangement of a conventionalelectric power control apparatus;-

FIG. 2 is a view showing the operating pointer of said conventionalelectric power control apparatus;

FIG. 3 is a block diagram showing the electric power control apparatusaccording to an embodiment of the present invention;

FIGS. 4 and 5 are block diagrams showing examples of the arrangementshown in FIG. 3, respectively;

FIG. 6 is a view showing the arrangement operating push-- FIG. 7 is acircuit diagram showing the principle of the timer circuit incorporatedin the arrangements of FIGS. 4 and 5;

FIGS. 8 and 9 are circuit diagrams showing circuit arrangementsconstructed in accordance with the principle of the timer circuit shownin FIG. 7, respectively; and

FIGS. 10 and 11 are circuit diagrams showing the electric power controlapparatus embodying the present invention, respectively.

Referring first to FIG. 3, numeral 1 represents an AC power source, 2 athyristor, 3 a load to which AC power is supplied in accordance with theconduction and nonconduction of the thyristor 2, and 4 a gate circuitadapted to control the amount of power supplied to the load 3 bychanging the trigger phase of the thyristor 2. Numeral 5 denotes a DCpower source, and 6 a timer circuit comprising a charge-dischargecircuit for the DC power source 5. The conducting time of the thyristoror the time during which power is supplied to the load is controlled bychanging the charging or discharging time of a condenser by selectingthe time constant of the timer circuit.

In theforegoing circuit arrangement, the timer circuit 6 operates tochange the charging or discharging time of a condenser by the selectedtime'constant to control the conducting time of the thyristor, thuscontrolling the time for which power is supplied to the load 3. The gatecircuit 4 operates to change the trigger phase of the-thyristor 4 tothereby control the amount of power supplied to the load 3. The changingof the power supplying time and amount is effected by means of variableelements selected by the push-switches.

FIG. 4 is a block diagram showing an example of FIG. 3, wherein the ACpower source 1 constitutes a closed circuit together with a main switch7, three-terminal bidirectional thyristor 2 (referred to as thyristorhereinafter) and load 3. Gate circuit 4 for the thyristor 2 is connectedbetween the second terminal 8 and the first terminal 10 of the thyristor2 through a switch means 9 which is operated by the timer circuit 6.Numeral 11 indicates a bidirectional trigger element (referred to astrigger element hereinafter), which is connected between the gatecircuit 4 and the gate terminal 12 of the thyristor 2.

In the foregoing circuit arrangement, upon closure of the main switch 7,a pulse determined by means of the gate circuit 4 and trigger element 11is applied to operate the thyristor 2 .with a phase determined by thegate circuit 4, so that a predetermined amount of power is supplied tothe load 3. After the lapse of the preset time, the timer circuit 6 isoperated to open the switch means 9 so that the trigger element 11 isstopped from providing the pulse. Thus the thyristor 2 interrupts thepower supply to the load 3.

FIG. 5 shows a circuit similar to that of FIG. 4, wherein partscorresponding to those of FIG. 4 are indicated by like numerals, exceptthat the switching means 9 operated by the timer circuit 6 is adapted tobe closed at the preset time of the timer circuit 6 to short circuit theoutput terminal of the gate circuit 4 so that the pulse generation bythe trigger element 11 is interrupted so as to stop the power supply tothe load 3 through the thyristor 2.

FIG. 6 shows an'example of the arrangement of pushbutton groups foroperating the gate circuit 4 and timer circuit 6 provided in FIGS. 3, 4and 5, the upper group being related to time setting and the lower groupto the control of power amount.

Numeral 13 represents an OFF" button for turning off the main switch andwhich is also adapted to returning pushbuttons l6 and 19 which aredepressed, to their original positions.

Numeral 14 indicates a continue button which is adapted to permit ofcontinued operation of the load when depressed. The pushbuttons 16, 17,18 and 19 are used to select the timeconstant elements for determiningtime limit in the timer circuit 6. The numerals 10, 20, 40 and 80indicated on these pushbuttons show the respective time limits insecond. By depressing the pushbuttons l6 and 18, for example, it ispossible not only to provide a time limit of 50 seconds (l0+40=50seconds) but also to separately provide time limits corresponding to therespective pushbuttons. This depends upon the arrangement of the timercircuit and the construction of the pushbuttons.

In order to use the timer circuit 6, the pushbuttons 16 to 19 aredepressed to set the time, and the timer circuit 6 is operated bydepressing the pushbutton 15, whereupon the required time limit starts.That is, the pushbutton is a STAR pushbutton. This button is returned tothe original position when released, whereas the main switch 7 remainsclosed. Furthermore, the pushbutton 15 is adapted to discharge thecharges stored at the capacitor of the timer circuit or close and thenimmediately open the circuit for charging the capacitor, prior toinitiation of charging or discharging.

The lower group of pushbuttons 20 to 29 are provided to control theamount of power supplied to the load. Any one of these pushbuttons islocked when depressed, so that a resistance of the required value in thegate circuit 4 is selected for controlling the trigger phase of thethyristor 2.

As will be appreciated from the foregoing, a required amount of power issupplied to the load for a desired period of time, by operating thepushbuttons. Thus, the control can be greatly facilitated, andrepetition can be easily performed, with a perfect reproducibility.

FIG. 7 illustrates the principle of the timer circuit 6 shown in FIGS. 4and 5, wherein a series circuit of a capacitor 30 and resistor 31 andthat of resistors 32 and 33 are connected in parallel with each otherbetween two points a and b, the connection points of these seriescircuits are indicated by c and d respectively and there is provided aPNP-type transistor 36 having the base 34 and emitter 35 thereofconnected with the points 0 and d, the collector being indicated by e.

In the foregoing circuit arrangement, if a DC voltage is applied betweenthe points a and b with the point a positive and the point b negative,then the potential at the capacitor 30 is zero at the initial stagesince there is no charge thereat. It is assumed that the voltage at thepoint d is V,, volts. It is also assumed that a voltage drop of V voltsoccurs between the base 34 and the emitter 35 of the transistor 36, andthat the voltage V, at the point 0 after t seconds will be representedby c d+ be (n Then, a signal appears between the points band e, wherebythe gate circuit 4 for the thyristor 2 can be operated. On theassumption that the values of the resistors 31, 32 and 33 and capacitor30 are R R R and C respectively, the following As will be seen from thisequation, the time t is proportional to the value R of the resistor 31or capacitance C of the condenser 30. Therefore, the time t can bechanged by changing either the value of R or C.

FIG. 8 is an example of the former case, wherein a series circuit ofresistors 38, 39, 40, 41 and 42 is inserted in place of the resistor 31shown in FIG. 7, normally closed switches 43, 44, 45 and 46 areconnected in parallel with these resistors respectively, and no suchswitch is connected with the resistor 38. These switches are adapted tobe actuated by pushbuttons 16, 17, 18 and 19 shown in FIG. 4respectively so that they are opened by depressing these buttons. Oneend of a resistor 47 is connected with the point 0 corresponding to thebase 34 of the transistor 36, and a nonnally open switch 48 is connectedbetween the other end of the resistor 47 and the terminal a.

Assume now that a DC voltage E is applied between the terminals a and band that normally closed switch 43 is opened. Then, charging of thecapacitor 30 is started, and the operating time of the transistor 36 isgiven by where R and R represent the values of resistors 38 and 39respectively. By providing small values for R and R 9. the followingexpression can be obtained:

be R1 E R.+R2 By opening the switches 43 and 45 at the same time, thefollowing expression can be obtained: ba RI t=.- (1239+ 11..) g. R1+ R2(5) That is, by opening the normally closed switches 43, 44, 45 and 46in combination, the time t can be increased in'correspondence to thecombination. In this case, the number of the normally closed switches isfour, and the total number of combinations is l5. Thus, it is possibleto set up 15 different time limits. Assume that the time limits obtainedby opening the respective switches are 10 seconds, 20 seconds, 40seconds and seconds as indicated on the pushbuttons 16 to 19 in FIG. 4respectively. Then, different time limits can be set up between 10seconds and 150 seconds with an interval of 10 seconds therebetween.

Thus, it is possible to set up a great number of time limit combinationsby selectively opening a plurality of such parallel circuits of normallyclosed switches and resistors which are connected in series with eachother.

If it is now assumed that the number of such parallel circuits is n,then it is possible to obtain (2 1 set time limits.

The resistor 38 serves to limit a current flowing between the emitter 35and the base 34 of the transistor 36 since there is a possibility thatthe transistor 36 is damaged by the fact that the current tends to beexcessively increased when the DC power source is supplied to thetransistor. In order to set up a new time limit after the lapse of acertain time limit, namely, in order to perform repetitive time limitsetting operation, it is essential to reduce the charges at thecondenser down to zero. For this purpose, there is provided a switch 48which is closed at a predetermined point of time so that the charges atthe condenser 30 are discharged therethrough, and a resistor 47 isprovided for preventing the discharge current from becoming excessive.

FIG. 9 shows a modified form of timer circuit 6 wherein resistors andswitches are connected in a different manner. In this example, normallyopen switches 43, 44, 45 and 46 provided in place of the normally closedswitches of FIG. 8 are selectively connected with the resistors 39, 40,41 and 42 respectively. Series circuits of the resistors 39, 40, 41 and42 and switches 43', 44', 45' and 46 are connected in parallel with eachother between the points c and b. The pushbutton structure is designedso that by depressing the button, one of the switches is closed and theremaining switches are opened so that only one switch is connectedbetween the points c and b. With such an arrangement, the number ofavailable time limits corresponds to the number of the series circuitsof the resistors and switches. This is sufficiently effective withrespect to certain applications, although it is less than the number ofthe combinations available in the caseof FIG. 8.

As described above, changing of the time constant can be effected bychanging the capacitance of the condenser 30. In order to change thetime constant by use of the pushbutton, this can be achieved by usingcondensers having different values and normally closed or open switches.It will be readily apparent that a similar circuit arrangement can beconstructed by using an NPN-transistor instead of the PNP-transistor 36.

FIGS. wand 11 show examples of the circuit embodying respectively. Thebase 60 of the transistor 53 is connected with the connection point i. Apoint j corresponds to the emitter of the transistor 53. By suitablyselecting the resistance values of the semifixed resistor 56, resistors57, 58 and 59 and relay coil 66, a certain voltage is applied betweenthe base and the emitter 55 of the transistor 53, so that the transistor53 is rendered completely nonconductive between the collector 54 and theemitter 55. In this example, the timer circuit 6 is constructed by theconnection enclosed by a dotted line and relay coil 66 and semifixedresistor 56 in such a fashion as to correspond to FIG. 8 tuned overlongitudinally through 180. The collector 62 of an NPN-transistor 61 isconnected to the point h, and the emitter 63 thereof is connected withthe point j. The respective resistors 38, 39, 40, 41, 42 and 47,switches 43, 44, 45, 46 and 48 and chemical condenser 30 of FIG. 8 areconnected in a manner completely reverse to that of FIG. 8. Diode 64 isconnected between the point c corresponding to the positive side of thechemical condenser 30 and the base of the transistor 61 with the anodethereof positioned at the base side of the transistor 61.

In operation, by closing the main switch 7 and normally open switch 52,a DC voltage is generated across the points a and b so that thetransistor 53 is rendered conductive as described above. As a result, acurrent is caused to flow through the relay coil 66 to close a contact67. In this case, the relay coil 66 is self-held even if the normallyopen switch 52 is opened. However, it isassumed that the switches 43,44,45 and 46 are opened in any combination. For example, if only theswitches 46 and 44 or the switch 45 is opened, then the sum of thevalues of the resistors 42 and 40 or the value of the resistor 41 isinserted between the points a and c, so that the potential at the base65 of the transistor 61 builds up in accordance with the chargingcharacteristic of the chemical condenser 30 depending upon theaforementioned resistance value upon application of a voltage betweenthe points a and b. When the base potential of the transistor 61 exceedsthe sum of the potential at the emitter thereof and the baseemittervoltage, a current is caused to flow from the collector 62 of thetransistor 61 to the emitter 63 thereof at the time represented byequation (2). Thus, the potential at the point h is decreased while thatat the point i is increased, so that the voltage between the base 60 andthe emitter 55 of the transistor 53 is rapidly decreased so that thelatter is rendered nonconductive. Consequently, the relay 66 opens thecontact 67. Thus, the DC power source circuit is stopped from providthepresent invention, respectively. FIG. 10 shows an example of FIG. 4, andFIG. 11 shows an example of FIG. 5.

Referring to FIG. 10, a closed circuit is constituted by an AC powersource 1, armature motor 148 (referred to as a motor hereinafter)serving as load 3, thyristor 2 and main switch 7, and it is the maincircuit for the motor 148. The phase and rotational frequency of themotor can be changed by means of the thyristor 2. Detailed descriptionwill now be made of the time limit setting circuit and trigger circuitfor determining the phase of the thyristor 2.

Timer circuit 6 is connected across the connection point f between theAC power source 1 and the motor 148 and the connection point g betweenthe main switch 7 and the second terminal 8 of the thyristor 2. V

DC power source 5 for the timer circuit includes a diode 49 having theanode thereof connected with the point f and the cathode connected withthe point g through a series circuit of a resistor 50, chemicalcondenser 51 and normally open switch 52. At this point, a DC voltageappears across the chemical condenser 51, with the positive side thereofat the point a and the negative side thereof at the point b.

Connected across the points a and b is a series circuit of a relay coil66, collector 54 of an NPN-transistor 53, emitter 55 thereof, semifixedresistor 56 and resistors 57, 58 and 59. These elements are arranged inthis order as viewed from the point a, h and 1' indicating theconnection point between the resistors 57 and 58 and between theresistors 59 and 58,

ing DC voltage, and the circuit arrangement is returned to the originalstate. The operating time of the relay 66 corresponds theoretically tothe time t determined from the foregoing equations 2, 3, 4 and 5. Thesemifixed resistor 56 is provided for the purpose of adjustment to makethe time t constant irrespective of any irregularity in the values ofall the components. The diode 64 serves to prevent any reverse voltagefrom being applied between the base 65 and the emitter 63 of thetransistor 61. Description will now be made of the powercontrollingportion, wherein connected between the terminal 10 of the thyristor 2and the point b are a series circuit of a condenser 68 and resistor 69and a series circuit of a condenser 70 and series circuits of resistors71 and and normally open switches 8l-to 90 connected in parallel witheach other, as in FIG. 1 5. A semifixed resistor 91 is connected betweenthe connection point k between the condenser 70 and the resistors 71 and80 and the point b, and a trigger element 11 is connected between thepoint k and the gate terminal 12 of the thyristor 2. Numeral 92indicates a resistor inserted between the connection point between thecondenser 68 and the resistor 69 and that between the condenser 70 andthe resistor 7 1.

In operation, by closing the normally open switch for example while thecontact 67 is closed by the relay 66, the value of the resistor 75 isinserted between the points b and It, so that an integrating circuit isconstituted by the resistor 75 and condenser 70. Thus, the triggerelement 11 is operated to permit the thyristor 2 to determine the amountof power to be supplied to the motor 148. The provision of the condenser68 and resistors 69 and 92 makes it possible to achieve a smallconduction angle which cannot be achieved merely by the use of theaforementioned integrating circuit. This means that supply of a lowpower is possible. When the contact 67 of the relay 66 is opened by thetimer circuit 6, the trigger element 11 is disabled to provide a signalso that the power supply to the motor 148 through the thyristor 2 isinterrupted.

The relationship between the foregoing power controlling portion and thepushbutton groups shown in FIG. 6 is as follows: By depressing theCONTINUE pushbutton 14, the switches 48 and 52 are closed so that thechemical condenser 30 is kept short circuited. Hence, there occurs novoltage buildup, and therefore the contact 67 is not opened eventuallyby the relay 66. The normally open switch 52 is so designed as to bereturned to the original position when the hand is removed therefrom.The normally open switch 52 is associated with the START" button 15, themain switch 7 with OFF button 13, and the normally closed switches 43,44, 45 and 46 with the pushbuttons 16, 17, 18 and 19 respectively.

The pushbuttons 20 to 29 of FIG. 6 are associated with the normally openswitches 81 to 90 respectively. The semifixed resistor 91 serves to makeconstant the amount of power supplied to the motor 148. It is possibleto set the conduction angle of the thyristor 2 to a desired value byclosing the normally open switch 81 and suitably turning the semifixedresistor 91.

As described above, the setting operation is simplified because of thepushbutton system, and a perfect reproducibility can be achieved by thefact that theamount and time of the power supply to the load are preset.Furthermore, accurate setting can be achieved, even in the case ofrepetitive use.

Even if the power supply is stopped and started again, the supply ofpower to the load is automatically interrupted because of the fact thatthe self-holding circuit of the relay 66 utilized. Thus, safety can beinsured. Further, the current flowing through the contact of the relay66 is the one which also flows through the gate circuit, DC power sourcecircuit and timer circuit, and therefore it is low enough to be able touse a relay having a low-contact capacity.

FIG. 11 shows .an example of FIG. 5, wherein a closed circuit isconstituted by the AC power source 1, motor 148, thyristor 2 and mainswitch 7, and normally open switch 93 and resistors 94 and 95 areconnected between the connection point f between the AC power source 1and the motor 148 and the connection point b between the main switch 7and the first terminal of the thyristor 2. A diode 96 is connectedbetween the connection point between the resistors 94 and 95 and a pointa, and a chemical condenser 97 is connected between points a and b.Thus, application of an AC voltage between the points f and b results ina DC voltage appearing between the points a and b. The points a and b ofthe timer circuit 6 shown in FIG. 6 are connected with theaforementioned points a and b respectively. When a preset point of timeis reached, therefore, a signal appears between the points e and b ofthe timer circuit 6. The purpose of this circuit is to interrupt thegate signal for the thyristor 2 by the use of the aforementioned signal.

An NPN-transistor 98 and PNP-transistor 99 are connected in parallelwith each other. The emitters 100 and 101 are short circuited with oneanother, and the collectors 102 and 103 lead to a point k through diodes104 and 105 respectively, with the cathode of the diode 104 coupled tothe collector 102 and the anode of the diode 105 to the collector 103.The point e is connected with the base 107 of the transistor 98 througha resistor 106 for limiting the amplitude of an input signal to asuitable level. The emitter 100 of the transistor 98, base 109 of thetransistor 99 and emitter of the latter are connected with the point bthrough a chemical condenser 108, resistor 110 and diode 111 having thecathode thereof coupled to the emitter 101, respectively.

A diode 112 is connected between the base 107 and the emitter 100 of thetransistor 98 with the cathode of the diode coupled to the base. Thetrigger circuit between the second terminal 8 of the thyristor 2-pointg-first terminal 10- point b is connected in the same manner as in thecase of FIG. 8. That is, one end of the condensers 68 and 70 isconnected with the point b, and these condensers are connected withConnected between the points k and g is semifixed resistor 91 g forcontrolling the lowest rotational frequency.

Description will now be made of the operation of this circuitarrangement. When a signal available from the timer circuit 6 issupplied between the points e and b, a current is caused to flow througha circuit constituted by resistor 106base 107 of the transistor98-emitter thereof-chemical condenser 108, so that the chemicalcondenser 108 begins to be charged with the emitter current amplified inthe transistor 98. At this point, if the AC voltage becomes positive atthe point k, then a current is caused to flow through the point k-diode104 collector 102 of the transistor 98--emitter 100 thereof chemicalcondenser 108-point b in the named order because of the fact that noresistance is present between the points k and b, so that the voltagebetween the points k and b is rapidly decreased.

When the AC voltage becomes positive at the point b, a current is causedto flow through a closed circuit consisting of the chemical condenser108-emitter 101 of the transistor 99- base 109 thereof-resistor110-point b because of the presence of charges at the chemical condenser108. As a result, an amplified current is caused to flow through thepoint bdiode Ill-emitter 101 of the transistor- 99collector 103thereof-diode -point k in the named order, so that the voltage betweenthe points b and k is rapidly decreased. Thus, a signal enters betweenthe points e and b, whereby the points k and b are short circuitedAC-wise. As will be seen from the above, the two transistors 98 and 99serve as AC switching means corresponding to the switch 9 shown in FIG.5, thus interrupting the power supply. The diode 112 is pro vided forthe purpose of protecting the transistor 98 by preventing a high-reversevoltage from being applied between the base 107 and the emitter 100 ofthe transistor 98 when the voltage appearing between the points k and bbecomes positive at the point b side.

As described above, the thyristor 2 is enabled to stop the motor 148after the lapse of a predetermined period of time by opening thenormally closed switches 43, 44, 45 and 46 in a predeterminedcombination. In this way, the adjustment of the amount of power andsetting of power supplying time can be achieved by actuating thepushbuttons even in the case where the relay is not employed. Especiallyin the circuit shown in FIG. 9, all the elements other than the switchesare completely contactless, and therefore the control device is of highdurability.

As will be appreciated from the foregoing, in accordance with thepresent invention, power supplied to a load is controlled by means of athyristor, and the control of the power supplying time is achieved bydetecting by means of transistors that a charge or discharge voltage ata condenser has become equal to a reference voltage to thereby renderoperative shorting circuit consisting of elements such as transistor andrelay or transistor and diode so as to control the gate circuit of thethyristor. It is particularly to be noted that all the operation fordetermining a time limit is performed by way of a pushbutton system.

The present invention has the following characteristics:

1. Because of the pushbutton system, the operation is simplified andfree from errors.

2. For the same time limit, the setting of it can be easily and quicklyeffected merely by depressing the START button.

3. The same time limit and rotational frequency can always be obtained.It is possible to void errors in adjustment and mechanical errors due toaging which tend to be involved in the prior art arrangement wherein apointer is turned to effect the desired control.

4. Because of the fact that the time-limit-setting up means is of thesumming system, a great number of combinations can be realized by meansof a small number of buttons.

5. Safety can be insured because in the case where use is made of arelay, even if the power source is cut off and then turned on while theapparatus is set to the operating condition, the motor is not rotated.

6. A high durability can be achieved because of the fact that theelements constituting the present apparatus except for the switches arecontactless ones such as transistors, resistors and condensers.

7. The time-limit setting can be simply and quickly effected byadjusting the voltage by rotating the semifixed resistor.

8. The time controlling operation can be silently performed without anynoise which tends to occur in a spring type one, because the timercircuit is constructed by the use of electronic components.

9. Because of the fact that the timer circuit is constructed by the useof electronic components, zero resetting can be achieved simply bydischarging charges stored at the condenser, thus resulting insimplified construction and operation. 1

What is claimed is: i

1. An electric power-controlling apparatus comprising a. a thyristorconnected in series with an AC power source and a load;

b. a timer circuit comprising first resistor means and first capacitormeans;

c. rectifier means connected between said timer circuit and said ACpower source, said rectifier means charging said first capacitor meansthrough said first resistor means, said timer circuit producing anoutput when said capacitor is charged or discharged to a predeterminedpotential;

d. a gate circuit comprising series-connected second resistor means andsecond capacitor means, said gate circuit generating a gate signalhaving a relative phase determined by the values of said second resistorand said second capacitor means;

e. a first transistor coupled to the output of said timer circuit andrendered conductive thereby;

. third capacitor means coupled to said first transistor for chargingtherethrough;

g. a second transistor having a polarity opposite that of said firsttransistor and connected in parallel therewith, said second transistorbeing rendered conductive by discharging said third capacitor meansthereby short-circuiting the output of said gate circuit; and

h. pushbutton switching means for selectively changing the resistancevalues of said first and second resistor means, said thyristor beingrendered conductive with a firing angle dependent on the relative phaseof said gate signal and being rendered nonconductive when the output ofsaid gate circuit is short circuited.

2. An electric power-controlling apparatus according to sistance circuitwhich are selectively and independently disconnectable from saidresistance circuit by said pushbutton circuit.

10 3. An electric power-controlling apparatus according to claim 2,wherein said first resistor means comprises a series circuit of saidplurality of resistors and said pushbutton circuit comprises a pluralityof pushbutton type normally closed switches which are respectivelyconnected in parallel with said resistors.

4. An electric power-controlling apparatus according to claim 1 whereinsaid gate circuit comprises a trigger element A for producing said gatesignal responsive to the voltage at the junction of said second resistormeans and said second capacitor, and said second resistor meanscomprises a plurality of parallel circuits, each having a series circuitincluding a resistor and a normally opened switch.

5. An electric power-controlling apparatus comprising a. a thyristorconnected in series with an AC power source 2 5 and a load;

b. a timer circuit comprising first resistor means and first capacitormeans;

c. rectifier means connected between said timer circuit and said ACpower source, said rectifier means charging said first capacitor meansthrough said first resistor means,

said timer circuit producing an output when said capacitor is charged ordischarged to a predetermined potential; d. a gate circuit comprisingseries-connected second resistor means and second capacitor means, saidgatev circuit generating a gate signal having a relative phasedetermined by the values of said second resistor and said secondcapacitor means;

. a relay having a coil coupled to said timer circuit and at least onecontact connected between said AC power source and said rectifier means,timer circuit and gate circuit, said relay contact being closed by theoperation of said timer circuit thereby energizing said timer forcontinued operation thereof after starting, said contact opening todeenergize said timer circuit after said timer circuit deenergizes saidrelay coil; and

. pushbutton switching means for selectively changing the resistancevalues of said first and second resistor means and for starting saidtimer circuit by connecting it to said AC power source, said thyristorbeing rendered conductive with a firing angle dependent on the relativephase of said gate signal and being rendered nonconductive by the outputof said timer circuit. 6. An electric power-controlling apparatusaccording to claim 5, wherein said gate circuit comprises a triggerelement for producing said gate signal responsive to the voltage at thejunction of said second resistor means and said second capacitor, andsaid second resistor means comprises a plurality of parallel circuits,each having a series circuit including a resistor and a normally openedswitch.

claim 1, wherein said timer circuit comprises a bridge circuit i UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3,638,091 Q t dJanuary 25, 1972 inventor) Tomo u i HOSOKAWA eta1 identified patentshown below: v

It is certified that error appears in the aboveand that said LettersPatent are hereby corrected as In the Claimfor Convention Priorityffiveof the six Japanese applications are omitted and should be included as.follows: Y

--'Japan, Appln. N9 43/85606 filed Nov. 25, 1968;

Japan, Appln. N 43/85607'filed Nov. 25, 1968; Japan, Appln. N 43/85608filed. Nov.- 25, 1968;

- Japan, Appln. N9 43/85609 filed Nov. 25, 1968; and Japan, Appln. N43/943 13 filed Dec. 19, 1968.

Signed and sealed this 15th day of August 1972;

' (SEAL) Attest:

EDWARD M.FLE'ICI-H*IR,JR.- 7 ROBERT GOTTSCHALK Attes-ting OfficerCommissioner of" Patents FORM PO-IOSO (10-69) USCOMM-DC 60376-P69 u.s.eovnuuzn'r manna omc: no o-au-nl UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent 1 Dated January 25, 1972 Inventor(s) yu HOSOKAWAeta1 It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

In the Claim for Convention Priority, five of the six Japaneseapplications are omitted and should be included as follows:

--'Japan, Appln. N9 43/85606 filed Nov. 25, 1968; Japan, Appln. N43/85607 filed Nov. 25, 1968; Japan, Appln. N 1 43/856053 filed Nov. 25,1968; Japan, Appln. N 43/85609 filed ,Nov. 25, 1968; and Japan, Appln. N43/943 13 filed Dec. '19, 1968.

Signed and sealed this 15th day of August 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. An electric power controlling apparatus comprising a. a thyristorconnected in series with an AC power source and a load; b. a timercircuit comprising first resistor means and first capacitor means; c.rectifier means connected between said timer circuit and said AC powersource, said rectifier means charging said first capacitor means throughsaid first resistor means, said timer circuit producing an output whensaid capacitor is charged or discharged to a predetermined potential; d.a gate circuit comprising series-connected second resistor means andsecond capacitor means, said gate circuit generating a gate signalhaving a relative phase determined by the values of said second resistorand said second capacitor means; e. a first transistor coupled to theoutput of said timer circuit and rendered conductive thereby; f. thirdcapacitor means coupled to said first transistor for chargingtherethrough; g. a second transistor having a polarity opposite that ofsaid first transistor and connected in parallel therewith, said secondtransistor being rendered conductive by discharging said third capacitormeans thereby short-circuiting the output of said gate circuit; and h.pushbutton switching means for selectively changing the resistancevalues of said first and second resistor means, said thyristor beingrendered conductive with a firing angle dependent on the relative phaseof said gate signal and being rendered nonconductive when the output ofsaid gate circuit is short circuited.
 2. An electric power controllingapparatus according to claim 1, wherein said timer circuit comprises abridge circuit including said first resistor means, said firstcapacitor, and a series circuit including two resistors and atransistor, a base of which is connected with the junction of said firstresistor means and said first capacitor and an emitter of which isconnected with the junction of said two resistors, and said firstresistor means includes a plurality of resistors forming a resistancecircuit which are selectively and independently disconnectable from saidresistance circuit by said pushbutton circuit.
 3. An electricpower-controlling apparatus according to claim 2, wherein said firstresistor means comprises a series circuit of said plurality of resistorsand said pushbutton circuit comprises a plurality of pushbutton typenormally closed switches which are respectively connected in parallelwith said resistors.
 4. An electric power-controlling apparatusaccording to claim 1 wherein said gate circuit comprises a triggerelement for producing said gate signal responsive to the voltage at thejunction of said second resistor means and said second capacitor, andsaid second resistor means comprises a plurality of parallel circuits,each having a series circuit including a reSistor and a normally openedswitch.
 5. An electric power-controlling apparatus comprising a. athyristor connected in series with an AC power source and a load; b. atimer circuit comprising first resistor means and first capacitor means;c. rectifier means connected between said timer circuit and said ACpower source, said rectifier means charging said first capacitor meansthrough said first resistor means, said timer circuit producing anoutput when said capacitor is charged or discharged to a predeterminedpotential; d. a gate circuit comprising series-connected second resistormeans and second capacitor means, said gate circuit generating a gatesignal having a relative phase determined by the values of said secondresistor and said second capacitor means; e. a relay having a coilcoupled to said timer circuit and at least one contact connected betweensaid AC power source and said rectifier means, timer circuit and gatecircuit, said relay contact being closed by the operation of said timercircuit thereby energizing said timer for continued operation thereofafter starting, said contact opening to deenergize said timer circuitafter said timer circuit deenergizes said relay coil; and f. pushbuttonswitching means for selectively changing the resistance values of saidfirst and second resistor means and for starting said timer circuit byconnecting it to said AC power source, said thyristor being renderedconductive with a firing angle dependent on the relative phase of saidgate signal and being rendered nonconductive by the output of said timercircuit.
 6. An electric power-controlling apparatus according to claim5, wherein said gate circuit comprises a trigger element for producingsaid gate signal responsive to the voltage at the junction of saidsecond resistor means and said second capacitor, and said secondresistor means comprises a plurality of parallel circuits, each having aseries circuit including a resistor and a normally opened switch.